Synthesis and optical properties of ZnO-ZnS core-shell nanotube arrays

Heterostructured ZnO-ZnS core-shell nanotube arrays with the diameters of 50-80 nm and lengths up to I mu m were synthesized by a two-step chemical reaction. First, the ZnO layer was grown by atomic-layer deposition. It was found that the preferred, growth orientation was strongly dependent on the substrate temperature. After sulfuration conversion from arrayed ZnO nanorods, the ZnS-ZnO composite arrays can be successfully prepared, as evidenced from transmission electron microscopy. This confirms that the ZnO-ZnS core-shell nanotube-arrayed structure has been fabricated. X-ray photoelectron spectroscopy analysis indicates that the binding energy of S 2p is the same as that of bulk single-crystal ZnS and that the Zn 2p(3/2) peak is shifted about 0.5 eV due to the formation of Zn-S bonds. Photoluminescence shows the relative-intensity ratio of ultraviolet emission (I-UV) to deep-level emission (I-DLE) for ZnO/ZnS core-shell nanotubes can be enhanced to be nine times that of original ZnO nanotubes. (c) 2006 American Vacuum Society.